Operating system and graphics card
Win 7, (CPU render)
Short description of error
Some frames in my file seems to have bug with motion blur, or something similar. Animation is done with explosion modifier and the pieces are very close of each other.
Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps
Not exactly sure what causes the problem, so here is the file and my Blender artists thread.